Tom Spring, age 13, is already busy designing his next must-have toy
A toy designed by a teenager from Leicestershire has proved to be a Christmas sell-out for the internet company who funded its production.
Tom Spring from Rothley said he has been left "speechless" by the success of his Putty Monsters creation.
Online retailer Firebox has reported sales of over 5,000 units since the product was launched in Summer 2010.
The 13-year-old saw his idea transformed to reality after winning a competition to find a "must-have" toy.
The toy consists of a lump of mouldable putty, available in various colours, complete with a set of wide staring plastic eyes.
People are encouraged to construct monster figures out of the set, take a photograph of their creations and then upload the image to the internet.
"I've always been trying to invent toys and I decided to mix my love of monsters, aliens and putty to create a toy out of it," said Tom.
Tom said his passion for inventing was partly inspired by his grandfather who worked for the Coalville-based company Palitoy, responsible for the internationally successful Action Man figure.
Gary Spring said he is very proud of his son's achievements and joked that he hoped Tom's inventions will allow him to retire early.
"I think it only really hits you when you go onto the Facebook site and you see all these people who are interacting and playing with something that your son's invented.
"That's when you have to pinch yourself a little bit," said Gary.
Tom is currently in the process of developing several new toy ideas, and has already submitted one creation to a major manufacturer.